diff --git a/src/context/typecore.ml b/src/context/typecore.ml
index 49b2f35ad7e..110e897e1a5 100644
--- a/src/context/typecore.ml
+++ b/src/context/typecore.ml
@@ -183,8 +183,18 @@ and monomorphs = {
 	mutable perfunction : (tmono * pos) list;
 }
 
+let pass_name = function
+	| PBuildModule -> "build-module"
+	| PBuildClass -> "build-class"
+	| PConnectField -> "connect-field"
+	| PTypeField -> "type-field"
+	| PCheckConstraint -> "check-constraint"
+	| PForce -> "force"
+	| PFinal -> "final"
+
 module TyperManager = struct
 	let create ctx m c f e pass params =
+		if pass < ctx.pass then die (Printf.sprintf "Bad context clone from %s(%s) to %s(%s)" (s_type_path ctx.m.curmod.m_path) (pass_name ctx.pass) (s_type_path m.curmod.m_path) (pass_name pass)) __LOC__;
 		let new_ctx = {
 			com = ctx.com;
 			g = ctx.g;
@@ -260,19 +270,19 @@ module TyperManager = struct
 		let c = create_ctx_c null_class in
 		let f = create_ctx_f null_field in
 		let e = create_ctx_e () in
-		create ctx ctx.m c f e PBuildModule en.e_params
+		create ctx ctx.m c f e PBuildClass en.e_params
 
 	let clone_for_typedef ctx td =
 		let c = create_ctx_c null_class in
 		let f = create_ctx_f null_field in
 		let e = create_ctx_e () in
-		create ctx ctx.m c f e PBuildModule td.t_params
+		create ctx ctx.m c f e PBuildClass td.t_params
 
 	let clone_for_abstract ctx a =
 		let c = create_ctx_c null_class in
 		let f = create_ctx_f null_field in
 		let e = create_ctx_e () in
-		create ctx ctx.m c f e PBuildModule a.a_params
+		create ctx ctx.m c f e PBuildClass a.a_params
 
 	let clone_for_field ctx cf params =
 		let f = create_ctx_f cf in
@@ -287,6 +297,14 @@ module TyperManager = struct
 	let clone_for_expr ctx =
 		let e = create_ctx_e () in
 		create ctx ctx.m ctx.c ctx.f e PTypeField ctx.type_params
+
+	let clone_for_type_params ctx params =
+		create ctx ctx.m ctx.c ctx.f ctx.e ctx.pass params
+
+	let clone_for_type_parameter_expression ctx =
+		let f = create_ctx_f ctx.f.curfield in
+		let e = create_ctx_e () in
+		create ctx ctx.m ctx.c f e PTypeField ctx.type_params
 end
 
 type field_host =
@@ -351,15 +369,6 @@ let type_generic_function_ref : (typer -> field_access -> (unit -> texpr) field_
 
 let create_context_ref : (Common.context -> ((unit -> unit) * typer) option -> typer) ref = ref (fun _ -> assert false)
 
-let pass_name = function
-	| PBuildModule -> "build-module"
-	| PBuildClass -> "build-class"
-	| PConnectField -> "connect-field"
-	| PTypeField -> "type-field"
-	| PCheckConstraint -> "check-constraint"
-	| PForce -> "force"
-	| PFinal -> "final"
-
 let warning ?(depth=0) ctx w msg p =
 	let options = (Warning.from_meta ctx.c.curclass.cl_meta) @ (Warning.from_meta ctx.f.curfield.cf_meta) in
 	match Warning.get_mode w options with
diff --git a/src/typing/generic.ml b/src/typing/generic.ml
index f3eb9eedc12..a0eebd9e8c3 100644
--- a/src/typing/generic.ml
+++ b/src/typing/generic.ml
@@ -26,7 +26,8 @@ let make_generic ctx ps pt debug p =
 				begin match c.cl_kind with
 					| KExpr e ->
 						let name = ident_safe (Ast.Printer.s_expr e) in
-						let e = type_expr {ctx with f = {ctx.f with locals = PMap.empty}} e WithType.value in
+						let ctx = TyperManager.clone_for_type_parameter_expression ctx in
+						let e = type_expr ctx e WithType.value in
 						name,(t,Some e)
 					| _ ->
 						((ident_safe (s_type_path_underscore c.cl_path)) ^ (loop_tl top tl),(t,None))
@@ -298,8 +299,10 @@ let build_generic_class ctx c p tl =
 			m_statics = None;
 			m_extra = module_extra (s_type_path (pack,name)) m.m_extra.m_sign 0. MFake gctx.ctx.com.compilation_step m.m_extra.m_check_policy;
 		} in
+		let ctx = TyperManager.clone_for_module ctx.g.root_typer (TypeloadModule.make_curmod ctx.com ctx.g mg) in
 		gctx.mg <- Some mg;
 		let cg = mk_class mg (pack,name) c.cl_pos c.cl_name_pos in
+		let ctx = TyperManager.clone_for_class ctx c in
 		cg.cl_meta <- List.filter (fun (m,_,_) -> match m with
 			| Meta.Access | Allow
 			| Final
diff --git a/src/typing/typeload.ml b/src/typing/typeload.ml
index fc8201b5648..5a2c33f0a52 100644
--- a/src/typing/typeload.ml
+++ b/src/typing/typeload.ml
@@ -279,7 +279,8 @@ let check_param_constraints ctx t map ttp p =
 			in
 			match follow t with
 			| TInst({cl_kind = KExpr e},_) ->
-				let e = type_expr {ctx with f = {ctx.f with locals = PMap.empty}} e (WithType.with_type ti) in
+				let ctx = TyperManager.clone_for_type_parameter_expression ctx in
+				let e = type_expr ctx e (WithType.with_type ti) in
 				begin try unify_raise e.etype ti p
 				with Error { err_message = Unify _ } -> fail() end
 			| _ ->
@@ -739,7 +740,7 @@ and type_type_params ctx host path p tpl =
 		tp,type_type_param ctx host path p tp
 	) tpl in
 	let params = List.map snd param_pairs in
-	let ctx = { ctx with type_params = params @ ctx.type_params } in
+	let ctx = TyperManager.clone_for_type_params ctx (params @ ctx.type_params) in
 	List.iter (fun (tp,ttp) ->
 		begin match tp.tp_default with
 			| None ->